It is known from the prior art that some microtechnical parts made of single crystal or polycrystalline materials are made by etching. This technique consists in taking the substrate to be etched and depositing a layer of photosensitive resin on top. A mask is placed on the resin and the whole assembly is exposed to light so that the photosensitive resin structure exposed to light is modified. This modified resin is eliminated by the action of a chemical element leaving the substrate bare at the places where the resin has been eliminated.
Subsequently, these bare regions of the substrate are chemically etched in order to create hollow portions. The chemical agent is chosen to etch only the material forming the substrate and not the unmodified photosensitive resin. The duration of this chemical etching step determines the dimensions of the hollow portions.
Similarly, it is possible to envisage making microtechnical parts by machining and/or polishing so that a drill or polisher may be used to form said parts.
A first drawback of this chemical etching technique is that it cannot produce hollow portions with vertical walls or sides. Indeed, the hollow portions obtained have inclined or rounded sides. This means that the surface of the hollow portion varies with depth, i.e. the surface becomes larger or smaller with the depth of the hollow. Generally the surface becomes smaller with depth. This observation means that theoretical calculations have to be adapted to obtain hollow portions with vertical sides. Further, this variation in the profile of the hollow portions between theory and practice results in a variation in characteristics.
A second drawback of these chemical etching or machining techniques is that they cannot create structures of complex depth. Indeed, chemical etching can only form hollow portions at the surface since the inclination of the sides means it is impossible to go deeper. For machining, the utilisation of a polisher and a drill are also unable to create complex inner structures. For example, the creation of a timepiece bearing made of single-piece ruby, i.e. formed of a single stone pierced with a blind hole, is possible, but the bearing cannot be lubricated unless the structures necessary for storing the lubricant are provided.